Utilization of melamine waste effluent

ABSTRACT

Thermally stable water soluble resins are prepared in a multistep process by reacting the waste solids from the mother liquor waste stream of a melamine manufacturing plant with an aldehyde and a sulfonating agent under controlled conditions of pH and temperature. The resin compositions are useful, for example, as superplasticizing agents for concrete mixtures, as mud drilling additives, and in the paper and textile industry. The process not only provides useful resin compositions, but also recovers solid wastes which are considered to be a major contributor to the pollution problems of melamine manufacturing plants.

BACKGROUND OF THE INVENTION

This invention relates broadly to the recovery of solid wastes from theeffluent stream generated in the manufacture of melamine and, moreparticularly, to the preparation of resin compositions from the solidwaste from the melamine industry, and to the use of such resincompositions as superplasticizers for admixture with concrete.

A major problem with most processes in the petrochemical industry is thecontamination of the effluent streams with various chemicals, includingunrecovered amounts of the primary product of the process. This isparticularly important in the case of the melamine industry.

Melamine is manufactured on a commercial scale by converting urea tomelamine in several stages, including a crystallization stage whichpurifies the melamine to the required specifications. The mother liquorfollowing the crystallization stage is normally stripped of ammonia andconcentrated to a solids content of about 1.5-5% by weight. This finaleffluent stream, which is usually disposed of as waste water, containsvarious proportions of melamine, oxyaminotriazines, cyanuric acid,melam, melan, melon, biuret, triuret, and other higher polycondensatesof urea and melamine. These various components, the percentages of whichvary depending on process conditions, are considered to be the majorcontributors to the pollution problems of melamine manufacturing plants.In addition to the pollution problems created by these waste solids, theactual tonnage of melamine lost in these waste solids is rathersubstantial. Accordingly, it would be most desirable from both aneconomic and ecological standpoint to recover the waste melamine andby-products in a commercially usable form.

The problem of recovering these waste materials has been dealt with byvarious melamine manufacturers and research organizations during recentyears. For example, it has been demonstrated that the solid content inthe effluent streams can be reduced by such varying techniques asbiological hydrolysis, thermal hydrolysis, absorption on activatedcarbon, the production of cyanuric acid from wasted melamine, and therecovery of the various waste products by means of ion exchangers. Whileall of the above techniques can reduce somewhat the solid content of thewaste effluent stream from a melamine process, none have been utilizedcommercially either because they are considered uneconomical ortechnically too complicated.

One such technique for reducing the melamine content in a waste effluentstream is taught in Kennedy, U.S. Pat. No. 3,496,176. In that patent, itis taught to adjust the pH of the mother liquor to 6-7, immediatelyafter the ammonia stripper, by bubbling carbon dioxide in the effluentstream. In this manner, about 70-80% of the ammelide and ammeline, i.e.,some of the by-products in the stream, are precipitated. The stream isthen filtered to remove the precipitated solids and melamine isrecrystallized from the filtrate. A similar procedure is disclosed inDakli et al, U.S. Pat. No. 3,423,411 to precipitate oxyandoxyaminotriazines, except that in the recovery of melamine it wasnecessary to heat the filtrate and then pass the heated filtrate througha column of cationic exchange resins to remove other nitrogen-containingorganic impurities and alkali ions. Still another technique for reducingthe melamine content of the waste stream is discussed in Fujiyoshi,Japanese Pat. No. 50-26553. In that patent it is disclosed to blend themother liquor from the melamine synthesis with cyanuric acid toprecipitate melamine and melamine cyanurate.

Hoogendonk, U.S. Pat. No. 3,496,177, relates to a process for thepurification of crude melamine by dissolving the crude melamine in waterafter adjusting the solution to a pH of 6-8, and then filtering at 105°C. The filtrate containing melamine is then adjusted to a temperature of50° C. and crystallization of pure melamine is obtained. A similarprocedure is disclosed in Rettler, German Pat. No. 1,162,379, exceptthat after dissolving the crude melamine in water, the solution istreated with a strongly basic ion exchange resin at 70°-75° C. beforethe solution is filtered and the melamine recrystallized. Elmer et al,U.S. Pat. No. 2,863,869, discloses purifying melamine in an aqueoussolution of sodium hydroxide (pH 11.5-11.9) at 129°-141° C., filteringthe solution, and then cooling to recrystallize the melamine.

It should be apparent from a review of the above and other knowntechniques for dealing with the problem of melamine plant waste thatefforts have been concentrated in the areas of:

(1) the recovery of the melamine waste from the waste effluent and itspurification to obtain high purity melamine;

(2) the recovery of the melamine waste from the waste effluent and itsutilization as feed material for manufacturing cyanuric acid ormelamine; and

(3) the treatment of the waste effluent as a pollutant and subjectingthe effluent to biological treatment.

Heretofore there have been no successful efforts to convert the solidwastes, i.e., the melamine together with the various by-products, thatare contained in the waste effluent into a commercially usable product,thereby improving the economics of the melamine synthesis plant whilesimultaneously reducing the plant's waste disposal problems.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an economically andecologically desirable process for recovering melamine and theby-products associated therewith from the waste effluent stream of amelamine process.

It is another object to reduce the solids content of a melamine processwaste effluent so as to reduce the pollution problems associated withthe disposal of such streams.

Still another object is to provide an economical process for preparinguseful resin compositions from the waste melamine and by-productscontained in the waste water from a commercial melamine synthesis plant.

Yet another object is to chemically treat the waste solids contained inthe waste water stream from a melamine manufacturing process to form awater soluble resin composition which has a variety of commercialapplications.

Still another object is to prepare a water soluble superplasticizingcomposition for use in concrete admixtures from the solids contained inthe waste effluent from a melamine synthesis plant.

These and other objects and advantages of the present invention areaccomplished by converting the waste melamine and by-product solidscontained in the effluent stream of a melamine synthesis plant intowater soluble resins which contain sulfonate groups. The conversionprocess may be carried out by the following sequence of steps:

(1) treating the waste solids from the waste water stream with analdehyde, suitably formaldehyde, for example, in the form of a formalinsolution (30-40%) at a temperature on the order of from about 40° C. toabout 80° C. after adjusting the pH to about 11-13;

(2) treating the solution obtained in step (1) with a sulfonating agent,such as a metal sulfite, bisulfite or metabisulfite, at a temperature offrom about 70° C. to about 90° C. for about 60 to about 180 minutes;

(3) polymerizing the reactive components of the solution from step (2)at a pH of about 1-5 and at a temperature on the order of from about 30°C. to about 80° C. for about 10 to about 150 minutes; and

(4) stabilizing the resulting resin solution by heating the same at a pHof from about 7-10 and a temperature of from about 50° C. to about 100°C. for about 30 to about 180 minutes.

The resulting sulfonated resin compositions are thermally stable watersoluble materials that can be used effectively and economically invarious applications such as, for example, as superplasticizers inconcrete admixtures, as drilling mud additives, in adhesives, in soilconditioners and stabilizers, in slow release fertilizers, and asadditives for the paper and textile industries.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic elevational view of a typical commercial highpressure melamine process plant; and

FIG. 2 is a schematic flow sheet and block diagram illustrating the lastprocessing steps involved in a typical melamine manufacturing plant.

DETAILED DESCRIPTION

In recent years, the prevailing method of producing melamine on acommercial scale has been based on urea as a starting material. Theconversion of urea to melamine can take place either at high pressure(Scheme I) or at low pressure over a catalyst (Scheme II). See W. S.Fong, Melamine, Report No. 122, SRI International, Menlo Park, Calif.(1978) and Melamine, Technical Leaflet: M5012, BASF (1970), both ofwhich are incorporated herein by reference.

The reaction sequence for the high pressure (Scheme I) and low pressure(Scheme II) processes are as follows:

    ______________________________________                                        SCHEME I                                                                      3(NH.sub.2).sub.2 CO                                                                        →                                                                             3HOCN + 3NH.sub.3                                                                              (1)                                     urea                 cyanic acid                                              3HOCN         →                                                                             (NCOH).sub.3     (2)                                                          cyanuric acid                                            (NCOH).sub.3 + 3NH.sub.3                                                                    →                                                                             C.sub.3 H.sub.3 N.sub.3 (NH.sub.2).sub.3 + 2H.sub.2                           O                (3)                                                          melamine                                                 3(NH.sub.2).sub.2 CO + 3H.sub.2 O                                                           →                                                                             6NH.sub.3 + 3CO.sub.2                                                                          (4)                                     SCHEME II                                                                     Catalyst                                                                      6(NH.sub.2).sub.2 CO                                                                        →                                                                             6HOCN + 6NH.sub.3                                                                              (5)                                                          cyanic acid                                              6HOCN         →                                                                             6HNCNH or        (6)                                                          H.sub.2 NCN + 3CO.sub.2                                                       carbodiimide                                                                  (cyanamide)                                              3H.sub.2 NCN or 3HNCNH                                                                      →                                                                             C.sub.3 H.sub.3 N.sub.3 (NH.sub.2).sub.3                                                       (7)                                                          melamine                                                 ______________________________________                                    

The temperatures at which the reaction must be carried out to obtainyields higher than 90% range between about 300° C. and 330° C. At lowertemperatures, biuret and cyanuric acid are the main products. Melaminedecomposes and deammoniates at temperatures above about 350° C., unlessit is stabilized with excess ammonia. The rate of the reactionnecessitates high temperatures; an optimum temperature range reported asbeing about 400° C. to about 430° C.

The theoretical conversion is about 0.35 kg of melamine, 0.28 kg ofammonia, and 0.37 kg of carbon dioxide per one kilogram of urea. Inpractice, however, the melamine yield is lower than that, about 90-95%of the theoretical yield. A rather wide variety of by-products formduring the reaction, including biuret, triuret, cyanuric acid, melaminecyanurate, melam, melan, melon, ureaidotriazine, ammeline, ammelide,hydroxytriazine and oxiaminotriazine. The concentrations of theseby-products depend to a large extent on reaction conditions.

The various commercial high pressure and low pressure catalyticprocesses are all similar in that they consist of three main sections orstages: melamine synthesis, melamine recovery, and off gas treatment andrecovery. In all of these processes, the reaction is carried out at atemperature range on the order of about 350° C. to about 400° C. underammonia to stabilize the melamine against decomposition. In the highpressure processes the reaction pressure is at least about 80atmospheres, whereas in the low pressure catalytic process, the reactionpressure generally is from about 1 to about 10 atmospheres.

Referring to FIG. 1, there is shown a schematic diagram of a typicalhigh pressure, liquid phase, non-catalytic process plant, wherein thereaction product is quenched with water to recover melamine, and ammoniaand carbon dioxide are produced as by-products. The conversion of ureato melamine is carried out at about 400° C. and 136 atm (2,000 psig) ina cylindrical reactor 10 that has a central draft tube surroundedconcentrically by a number of electrical bayonet heaters. Molten urea,fed from a surge track 11 into the reactor below the draft tube throughline 12 circulates upward outside the draft tube and then downwardinside the draft tube. The product effluent, withdrawn from the topsection of the reactor through line 13 is charged into a quench tank 14where it is cooled with process water. The resulting aqueous slurry isthen fed through line 16 into the top of a carbon dioxide stripper 17 toproduce an aqueous slurry of crude melamine. The off-gas from the quenchtank and from the stripper are exported as by-products through line 18.The off-gas in line 18 contains ammonia, carbon dioxide and water vapor.The aqueous slurry of crude melamine from the stripper 17 is fed to acrude slurry tank 19, whereafter it is mixed with liquid ammonia andpassed through a heater 21 and into a hydrolyzer 22. The liquid ammoniais mixed with slurry of crude melamine by adding the ammonia throughline 23 adjacent the inlet of the heater 21 and the heater effluent ispassed through line 24 into the hydrolyzer 22. By heating the slurry ofcrude melamine in the presence of ammonia, the melamine is dissolved andsome of the impurities are hydrolyzed to insolubles such ashydroxytriazines. The overhead effluent from the hydrolyzer 22 is thenpassed through a filter 26 to remove the insolubles, and then throughline 27 into an activated carbon bed 28 to remove color-causing matter.The solution is then passed via line 29 through another filter 31 beforeit is cooled in a recrystallization system comprised of thecrystallization tank 32 and crystallizer 33 to recrystallize themelamine.

The recrystallized melamine, harvested by means of centrifuges 34, arefed through line 36 to a drier 37. The dried melamine product is thenconveyed by air to appropriate product bins 38.

The mother liquor from the centrifuges 34 is fed through line 39 to anammonia column feed tank 41, and from the feed tank 41 through line 42to the ammonia column 43, to recover ammonia. The gaseous ammonia whichis recovered as overhead from the ammonia column 43 is condensed andcollected in the condenser 44 from which it is recycled for admixturewith the slurry of crude melamine adjacent the inlet of heater 21. Thebottoms from the ammonia column 43 comprises the waste water whichcontains the residual melamine and by-products which normally are fed toa pollution plant through line 46, but which now are to be treated andrecovered in accordance with the present invention.

About 3.3 kg of urea and 0.1 kg of ammonia are reportedly consumed toproduce 1.0 kg of melamine and 1.1 kg of ammonia by-product in the formof an ammonia-carbon dioxide-water mixture. The melamine yield is about86.6% of the theoretical yield based on urea for this process.

The process described above in connection with FIG. 1 is the processknown as the Allied Chemical melamine process. Other similar highpressure non-catalytic commercial processes are practiced by the NissanChemical and Montecatini Edison. Several companies have developedcommercial low pressure catalytic processes and among them areChemico-USS Chemical, Chemie Lenz, Stamicarbon, and BASF. Of thesevarious known commercial processes for producing melamine theStamicarbon process and the Chemie Lenz process employ a melaminerecovery and purification section which are quite similar to sectionused in the hereindescribed Allied Chemical process. In the NissanChemical process, the liquid product from the reactor is aged, and thenquenched with water and ammonia to produce an aqueous ammonia solutioncontaining melamine. The purity of the product and yield depend upon thepercentage of ammonia in the solution. The aqueous ammonia is then sentto a stripper where the ammonia is removed and the melamine is recoveredfrom the solution by crystallization, centrifugation and drying.

In the BASF process, the reaction solution is passed through filters toremove waste solids, whereafter the filtrate is quenched and sent to aspecially designed cyclone to separate the melamine.

In all of the known commercial processes, the waste water effluent fromthe melamine recovery and purification section contains residualmelamine and various by-products which can be treated in accordance withthe present invention. A block diagram illustrating the last processingsteps involved in a typical melamine manufacturing plant is shown inFIG. 2, and an analysis of the waste solids contained in the motherliquor waste stream from that plant is shown in Table I. As shown inTable I, the waste solids in the mother liquor waste stream is composedof 20-30% by weight of oxyaminotriazines, 0.1-1.0% by weight ofploycondensates, 70-75% by weight of melamine and 0-6% by weight of ureaand urea polycondensates.

                  TABLE I                                                         ______________________________________                                        ANALYSIS OF THE SOLID CONTENT OF                                              THE WASTE WATER STREAM.sup.e                                                  Composition of                                                                Effluent Stream Sample 1.sup.a                                                                             Sample 2.sup.a                                   ______________________________________                                        Total Solids    3.37 g.      1.80 g.                                          Melamine        69.7%        70.6%                                            Oxytriazines.sup.b                                                                            29.7%        23.3%                                            Polycondensates.sup.c                                                                         0.6%         0.5%                                             Others.sup.d    --           5.6%                                             ______________________________________                                         .sup.a Samples taken at different intervals of plant operation.               .sup.b Oxytriazines include ammeline, ammelide and cyanuric acid.             .sup.c Polycondensates include mainly melam, melan, and melon.                .sup.d Urea and urea polycondensates.                                         .sup.e At present, complete analysis and exact determination of the           concentration of each compound found in the waste solid, such as ammeline     ammelide, melam, melon, etc., is difficult. Present analytical procedures     provide only the percentages for melamine, the oxyaminotriazines              (ammeline, ammelide, and cyanuric acid, collectively) and the                 polycondensates (melam, melem, melon, etc., collectively).               

The melamine and by-products are, for the most part, contained in themother liquor waste stream in colloidal form.

According to the present invention, the mother liquor, preferably afterthe water recovery step shown in FIG. 2, is processed to separate asmuch of the solids content as possible within the bounds of economics.This separation can be accomplished, for example, by filtering,centrifuging or sedimenting the mother liquor waste stream directly, orby first treating the stream with a flocculating agent such as sulfuricacid, carbon dioxide or other flocculating agents commonly used in watertreatment, and then filtering, centrifuging or sedimenting. By using theabove separation techniques, the solids would be separated in the formof a paste having a variable water content which could be controlled,for example, by subsequent mechanical or thermal drying processes.Alternatively, the solids content of the mother liquor waste streamcould be separated by spray drying or by evaporating the water therefromcompletely or partially.

The solid or paste obtained through the above procedure is then reactedwith an aldehyde, preferably formaldehyde, in a multistep process whichresults in the formation of stable water soluble resinous materials thatare suitable for use in a variety of applications, such as in drillingmuds, adhesives, molding and laminate compounds, and paper and textiletreating compounds. The resinous materials prepared in accordance withthis invention are particularly well suited for use as superplasticizingagents which impart improved workability and flowability to concretemixtures.

The water soluble resinous materials of the present invention areprepared by reacting the melamine and by-product-containing paste orsolids obtained from the mother liquor waste stream with the aldehyde inthe following sequence of steps:

(a) a solution of the aldehyde, preferably formaldehyde, having aconcentration on the order of from about 30% to about 40% by weight isadjusted to a pH value of from about 11.0 to about 13.0 by the additionof aqueous alkali metal hydroxide. The alkaline solution is heated toabout 40° C.-80° C. and a quantity of the waste solids or paste is addedto the solution such that the ratio of waste solids: aldehyde is in therange of from about 0.8:1 to about 1.6:1. The mixture is maintained atthe above temperatures for a period of from about 10 to about 60 minuteswhile being agitated;

(b) to the above solution, a sulfonating agent such as an alkali metalsulfite, bisulfite or metabisulfite is added such that the molar ratioof aldehyde to sulfite group is from about 2.5:1 to about 5.0:1, and thetemperature of the reaction mass is raised to from about 70° C. to about90° C. and maintained at that temperature for about 60 to 180 minutes.During this period, the pH of the reaction mass is maintained in therange of from about 11.0 to about 13.0 by adding an alkaline hydroxide,preferably an alkali metal hydroxide solution as necessary;

(c) the temperature of the solution from step (b) is then readjusted toabout 30° C.-80° C. and an acid solution, preferably a sulfuric acidsolution, is added to lower the pH to about 1.0-5.0. The reaction massis then kept under these conditions with continuous agitation for about30 to 180 minutes;

(d) the pH of the reaction mass is then raised to about 7.0 to about10.0 and the temperature is adjusted to about 50° C.-100° C. Thereaction mass is maintained under these conditions with constantagitation for about 30 to 180 minutes, whereafter the reaction mass iscooled to ambient temperatures, adjusted to a pH of about 8.0-13.0, anddiluted to a solids content as required for the intended application.Usually, a solids content of from about 5%-50% is desired, with amountsranging from about 10%-30% by weight being preferred forsuperplasticizer applications.

The invention will be more fully understood in light of the followingexamples, all of which are given for illustrative purposes only and notfor the purposes of limiting the scope of this invention.

EXAMPLE 1

A ten liter sample of the mother liquor waste water stream of a melaminemanufacturing plant was heated at 110° C. until all of the waterevaporated. The weight of the remaining solid was found to be 180 g. Asample of this solid was analyzed by standard spectrophotometric andgravimetric analytical techniques to determine the percentages ofpolycondensates, oxyaminotriazines and urea condensates. The resultswere found to be 0.5%, 23.3% and 5.6%, respectively. The remainingcomponents of the solid is melamine which amounts to 70.6%.

EXAMPLE 2

A one liter sample of the mother liquor waste water stream of a melaminemanufacturing plant was heated at 110° C. until all of the waterevaporated. The weight of the solid remaining following evaporation is21.5 g. The elemental composition of this solid was determined bystandard analytical techniques to be as follows: N, 60.04%; C 30.48%; H,4.49%. The theoretical elemental composition for melamine is: N, 66.6%;C, 28.57%; H, 4.76%, and that for ammeline is: N, 55.12%; C, 28.35%; H,3.94%.

EXAMPLE 3

A ten liter sample of the mother liquor from a typical melaminemanufacturing plant was filtered to recover the solids contenttherefrom. The solids were analyzed and were found to containapproximately 69.7% by weight of melamine, 29.7% by weight ofoxytriazines (ammeline, ammelide, and cyanuric acid, collectively), and0.6% by weight of polycondensates (melam, melem, melon, etc.,collectively). A quantity of paraformaldehyde (94.6% formaldehyde byweight) weighing 50.34 g. was mixed with 230 ml of water which was madebasic by the addition of NaOH solution, and was heated at 55° C. for 30minutes with continuous agitation. The pH of the solution was adjustedto 12.00 and an additional quantity of water (88 ml) was added. Thesolution temperature was adjusted to 45° C. and 50 g. of the solidobtained from the mother liquor was added. Agitation was continued for15 minutes. A quantity of 37.7 g. of sodium metabisulfite and 12 ml ofwater were then added to the reaction solution. The reaction wascontinued at 78° C. for 120 minutes. The temperature was then lowered to45° C. and the pH was adjusted to 3.0 by adding 30 ml of H₂ SO₄ (14.5molar). The reaction solution was agitated under these conditions for 60minutes, then its pH was raised to 7.0 using NaOH solution and thetemperature was raised to 78° C. with continuous agitation. The solutionwas kept under these final conditions for 60 minutes. The solution wasdiluted to 20% resin content after adjusting its pH to 11.0 and itsviscosity at 20° C. was found to be 3.7 cp. A sample of the abovesolution was found to be very stable compared to commercial sulfonatedmelamine formaldehyde products at 60° C.

EXAMPLE 4

A formalin solution was prepared in a manner analogous to that describedin Example 3. The pH of the solution was adjusted to 12.0 and 88 ml ofwater were added. Keeping the temperature of the solution at 55° C., 50g. of the solid obtained from the mother liquor of Example 1 was addedand agitated for 15 minutes. A quantity of 37.7 g. of sodiummetabisulfite and 12 ml of water were then added to the reactionsolution. The solution was heated to 78° C. and kept at this temperaturefor 120 minutes with constant stirring, then the temperature was loweredto 70° C. and the pH to 3.0. The reaction solution was agitated underthese conditions for 150 minutes, then the pH was raised to 7.0 and thetemperature to 78° C. for 60 minutes. The final solution was adjusted topH 10.5 and its solid content was 26.4%. The viscosity of final solutionafter dilution to 20% solid content at 20° C. was found to be 5.6 cp.

EXAMPLE 5

The resin solution prepared according to Example 3 was found to be acement superplasticizer. The resin solution was examined according toASTM C-187-79, C-109-79 and C-191-79, to determine its effect onwater/cement ratio, compressive strength, and setting times,respectively. The results of these tests in comparison with analogoustests done on neat cement mortar mix, as well as on a mix containing acommercial melamine-based superplasticizer^(l), are shown in Table 2.The results indicate that for the same slump² of 15.5 ±0.5 cm, acompressive strength improvement of 37% over the results obtained forthe neat mix is found when 3% of the resin solution by weight of cementis used.

                                      TABLE 2                                     __________________________________________________________________________    PROPERTIES OF RESIN SOLUTION OF                                               EXAMPLE 3 AS ADDITVE FOR CEMENT MORTAR                                               % Weight of                                                                   Admixture             Setting Time                                                                         Compressive Strength                             Solution Water                                                                              Water   (min)  (kg/cm.sup.2)                                    Weight of Cement                                                                       Cement                                                                             Reduction (%)                                                                         Initial                                                                           Final                                                                            1 day                                                                             3 days                                                                            7 days                                                                            28 days                       __________________________________________________________________________    Neat   --       0.23 0.0     180 240                                                                               85 167 228 303                           Resin of                                                                             1.0      0.215                                                                              6.5     165 180                                                                              --  --  --  --                            Example 3                                                                            3.0      0.185                                                                              19.6    225 240                                                                              115 213 264 416                                  5.0      0.165                                                                              28.3    345 360                                                                              --  --  --  --                            Commercial                                                                           1.0      0.22 4.35    180 205                                                                              --  --  --  --                            Super- 3.0      0.185                                                                              19.6    225 240                                                                              171 254 288 412                           plasticizer                                                                          5.0      0.16 30.4    270 285                                                                              --  --  --  --                            __________________________________________________________________________

EXAMPLE 6

The properties of the resin solution prepared by Example 3 as a concreteadditive were studied. A concrete mix consisting of cement 385 parts,water 205 parts, sand (zone 3) 625 parts, aggregate (10 mm) 395 parts,aggregate (20 mm) 795 parts and 11.55 parts of resin solution fromExample 3 was prepared. This was compared with a similarly prepared neatmix containing no resin and with a mix containing 11.55 parts of thecommercial melamine-based concrete superplasticizer liquid Melment L-10having 20% solid content. The results of these tests are shown in Table3

                  TABLE 3                                                         ______________________________________                                        COMPRESSIVE STRENGTHS DATA OF CONCRETE -                                      NEAT, WITH RESIN SOLUTION OF EXAMPLE 3,                                       AND WITH A COMMERCIAL SUPERPLASTICIZER                                                          Compressive strength (kg/cm.sup.2)                                 Slump Water      1            7    28                                         (mm)  reduction (%)                                                                            day    3 days                                                                              days days                                ______________________________________                                        Neat     51       0         126  239   268  357                               3% Resin 60      29         236  381   515  615                               of                                                                            Example 3                                                                     Commercial                                                                             40      29         241  373   457  531                               Superplas-                                                                    ticizer                                                                       ______________________________________                                    

EXAMPLE 7

The stability of the resin solution prepared according to Example 3 wascompared with a commercial melamine-based concrete superplasticizer,Melment L-10. The resin solution prepared according to this inventionshowed greater stability, i.e., smaller changes in pH and viscosity, incomparison with the commercial sample, when subjected to a constanttemperature of 60° C. for 14 days. The results are shown in Table 4.

                  TABLE 4                                                         ______________________________________                                        COMPARISON OF THE STABILITY OF pH AND                                         VISCOSITY OF PREPARED RESIN OF EXAMPLE 3                                      AND COMMERCIAL MELAMINE-BASED RESIN                                                    Resin Solution  Commercial                                           Time     of Example 3    Resin Solution                                       (days)   pH       Viscosity (cp)                                                                           pH     Viscosity (cp)                            ______________________________________                                        0        10.99    3.70       11.30  4.27                                      2        10.38    3.68       9.40   3.92                                      6        9.90     3.64       8.90   3.13                                      8        9.85     3.68       8.99   2.88                                      10       9.63     3.83       8.80   2.76                                      14       9.31     4.05       8.75   2.72                                      Percent  15.37%   9.5%       22.6%  36.3%                                     Change from                                                                   Initial                                                                       Value                                                                         ______________________________________                                    

While the invention has been described herein in connection with certainembodiments and certain structural and procedural details, it is clearthat changes, modifications or equivalents can be envisioned by thoseskilled in the art; accordingly, such changes within the principles ofthe invention are intended to be included within the scope of the claimsbelow.

What is claimed is:
 1. A process for preparing water soluble sulfonategroup-containing resin materials from the waste solids from the motherliquor waste effluent stream of a melamine manufacturing plant, whichcomprises:(a) separating the waste solids from the mother liquor wasteeffluent stream from a melamine manufacturing plant; (b) treating theseparated solids at a temperature of about 40° C.-80° C. and for aperiod of from about 10 to about 60 minutes with an aldehyde solutionhaving a pH of about 11.0-13.0, said waste solids and said aldehydesolution being present in respective amounts such that the weight ratioof waste solids: aldehyde is from about 0.8:1 to about 1.6:1; (c)sulfonating the aldehyde treated waste solids at a temperature in therange of about 70° C.-90° C. for a period of from about 60 to about 180minutes and at a pH of about 11.0-13.0 by adding a sufficient amount ofsulfonating agent to the reaction mass to provide a molar ratio ofaldehyde:sulfonating group of about 2.5:1 to 5:1, said pH being adjustedby the addition of an alkaline hydroxide; (d) readjusting thetemperature of the reaction mass to about 30° C.-80° C. and the pHthereof to about 1.0-5.0, and maintaining these conditions underagitation for a period of from about 10 to about 150 minutes topolymerize the reactive materials contained in said reaction mass; and(e) readjusting the temperature of the reaction mass to about 50°C.-100° C. and the pH thereof to about 7.0-10.0, and maintaining theseconditions under agitation for a period of from about 30 to about 180minutes to stabilize the soluble resin materials contained therein. 2.The process of claim 1, further comprising the step of cooling the finalreaction mass to ambient temperatures and adjusting the pH thereof toabout 8.0-13.0.
 3. The process of claim 2, wherein said aldehyde isformaldehyde.
 4. The process of claim 2, wherein said sulfonating agentis selected from the group consisting of alkali metal sulfites, alkalimetal bisulfites and alkali metal metabisulfites.
 5. A process forpreparing water soluble resins from waste solids from the mother liquoreffluent stream from melamine manufacturing plants, which comprise:(a)treating the waste solids from the effluent stream with an aldehydesolution at a temperature of about 40° C.-80° C. after adjusting the pHof said solution to about 11.0-13.0; (b) sulfonating the solution fromthe preceding step at a temperature of about 70° C.-90° C. for about 60to 180 minutes with a sulfonating agent selected from the groupconsisting of alkali metal sulfites, alkali metal bisulfites and alkalimetal metabisulfites; (c) polymerizing the reactive components containedin the sulfonated solution of the preceding step at a pH of 1.0-5.0 andat a temperature of 30° C.-80° C. for about 10 to about 150 minutes; and(d) stabilizing the resulting resin solution by heating the same at a pHof about 7.0-10.0 and at a temperature of about 50° C.-100° C. for about30 to 180 minutes.
 6. The process of claim 5, wherein said aldehyde isformaldehyde, wherein the weight ratio of waste solids to formaldehydeis from about 0.8:1 to about 1.6:1, and wherein the molar ratio offormaldehyde to sulfite groups is from about 2.5:1 to about 5.0:1. 7.The process of claim 6, wherein said stabilized resin solution isadjusted to a pH of about 8.0-13.0 and cooled to ambient temperatures.8. The process of claim 7, wherein said stabilized resin solution isdiluted to a solids concentration on the order of about 10-30% byweight.
 9. A process for treating the waste water effluent stream ofmelamine manufacturing plants and reducing the amount of pollutantscontained therein, which comprises:(a) separating the waste solids fromthe mother liquor waste effluent stream from a melamine manufacturingplant; (b) treating the separated solids at a temperature of about 40°C.-80° C. and for a period of from about 10 to about 60 minutes with analdehyde solution having a pH of about 11.0-13.0, said waste solids andsaid aldehyde solution being present in respective amounts such that theweight ratio of waste solids:aldehyde is from about 0.8:1 to about1.6:1; (c) sulfonating the aldehyde treated waste solids at atemperature in the range of about 70° C.-90° C. for a period of fromabout 60 to about 180 minutes and at a pH of about 11.0-13.0 by adding asufficient amount of sulfonating agent to the reaction mass to provide amolar ratio of aldehyde:sulfonating group of about 2.5:1 to 5:1, said pHbeing adjusted by the addition of an alkaline hydroxide; (d) readjustingthe temperature of the reaction mass to about 30° C.-80° C. and the pHthereof to about 1.0-5.0, and maintaining these conditions underagitation for a period of from about 10 to about 150 minutes topolymerize the reactive materials contained in said reaction mass; and(e) readjusting the temperature of the reaction mass to about 50°C.-100° C. and the pH thereof to about 7.0-10.0, and maintaining theseconditions under agitation for a period of from about 30 to about 180minutes to stabilize the soluble resin materials contained therein. 10.The process of 9, further comprising the step of cooling the finalreaction mass to ambient temperatures and adjusting the pH thereof toabout 8.0-13.0.
 11. The process of claim 9, wherein said aldehyde isformaldehyde.
 12. The process of claim 9, wherein said sulfonating agentis selected from the group consisting of alkali metal sulfites, alkalimetal bisulfites, and alkali metal metabisulfites
 13. A process fortreating the waste water effluent stream of melamine manufacturingplants and reducing the amount of pollutants contained therein, whichcomprises:(a) separating the waste solids from the waste water effluentstream from a melamine manufacturing plant; (b) treating the separatedwaste solids with an aldehyde solution at a temperature of about 40°C.-80° C. after adjusting the pH of said solution to about 11.0-13.0;(c) sulfonating the solution from the preceding step at a temperature ofabout 70° C.-90° C. for about 60 to about 180 minutes with a sulfonatingagent selected from the group consisting of alkali metal sulfites,alkali metal bisulfites, and alkali metal metabisulfites; (d)polymerizing the reactive components contained in the sulfonatedsolution of the preceding step at a pH of 1.0-5.0 and at a temperatureof 30° C.-80° C. for about 10 to about 150 minutes; and (e) stabilizingthe resulting resin solution by heating the same at a pH of about7.0-10.0 and at a temperature of about 50° C.-100° C for about 30 toabout 180 minutes.
 14. The process of claim 13, wherein said aldehyde isformaldehyde, wherein the weight ratio of waste solids to formaldehydeis from about 0.8:1 to about 1.6:1, and wherein the molar ratio offormaldehyde to sulfite groups is from about 2.5:1 to about 5.0:1. 15.The process of claim 14, wherein said stabilized resin solution isadjusted to a pH of about 8.0-13.0 and cooled to ambient temperatures.16. The process of claim 15, wherein said stabilized resin solution isdiluted to a solids concentration on the order of about 10%-30% byweight.
 17. A thermally stable resin solution prepared in accordancewith the process of claim
 1. 18. A thermally stable resin solutionprepared in accordance with the process of claim
 5. 19. A thermallystable resin solution prepared in accordance with the process of claim6.
 20. A thermally stable resin solution prepared in accordance with theprocess of claim 8.